(1) Field of the Invention
The present invention relates to nut feeding methods and nut feeders.
(2) Description of Related Art
An exemplary nut feeder adopted for nut resistance welding or other purposes is disclosed in Japanese Unexamined Patent Application Publication No. 2005-111559. The nut feeder includes a feed rod provided at its front end with a small-diameter portion insertable into the screw hole of a nut and a supply tube for supplying nuts to this feed rod. For this nut feeder, a nut is delivered toward the front of the feed rod put on standby through the supply tube, the feed rod is set in motion and thus moves forward so that the small-diameter portion is inserted into the screw hole of the nut, and the nut is fed as it is to an intended position, such as the position of a part of a workpiece to which the nut is to be welded.
Meanwhile, when an abnormal nut having a smaller diameter than a normal nut is delivered from a nut delivery unit, such as a supply tube, this abnormal nut needs to be prevented from being fed to the intended position. To cope with this, the following technique is disclosed in Japanese Patent No. 3309245: When an abnormal nut whose thread hole has a smaller diameter than a small-diameter front-end portion of a feed rod is delivered toward the front of the feed rod, the small-diameter front-end portion cannot be inserted into the screw hole, and therefore the abnormal nut is flicked forward by the small-diameter front-end portion so as to be prevented from being fed to an intended position.
Furthermore, the following technique is disclosed in Japanese Unexamined Patent Application Publication No. 2006-75899: A shoulder between a large-diameter basal portion of a feed rod and a small-diameter front-end portion thereof engages with a nut subsequent to an abnormal nut, thereby blocking the forward movement of the feed rod and thus preventing the feed of the abnormal nut.